The present invention relates to a an airplane distress system and, more particularly, to a distress system to assist in identifying airplanes that have been taken over by presumed hijackers.
Avionics that are currently available and installed in most aircraft include a transponder that transmits a signal to the Air Traffic Control (ATC). Prior to each flight, the pilot is given a discrete 4-digit code. The transponder code is linked to the ATC ground radar system and follows the airplane to its destination. There are certain 4-digit codes that a pilot can tune into the transponder under certain emergency circumstances. Examples include:    7700 Emergency (this code also causes the ATC system to send out an alarm signal)    7600 Communications failure    7500 Hijack situation
In the situation that occurred on Sep. 11, 2001, it is understood that none of the airplanes that were taken over had their transponder tuned to 7500. This would mean that the hijackers gained control of the cockpit without time for the pilot to tune the transponder to 7500, or that the hijackers themselves turned off the transponder.